Journal of Bridge Engineering

This paper presents a real-time dynamic substructuring (RTDS) test program that was carried out on a bridge structure equipped with seismic isolators with self-centering and friction energy dissipation capabilities. The structure studied also included bearing units with sliding interfaces providing additional energy dissipation capacity. In the RTDS tests, the seismic isolator was physically tested in the laboratory by using a high performance dynamic structural actuator imposing, in real time, the displacement time-histories obtained from numerical simulations that were run in parallel. The integration scheme used in the test program was the Rosenbrock-W variant and the integration was performed by using the MathWorks’s Simulink and an XPC target computer environment. The numerical counterpart included the bridge piers and the additional energy dissipation properties. The nonlinear response of these components was accounted for in the numerical models. The RTDS tests were performed in the direction parallel to the length of the bridge. The effects of various ground motions and the influence of modeling assumptions such as friction and column stiffness were investigated. Finally, the test results were compared to the predictions from dynamic time-history analyses performed by using commercially available computer programs. The results indicate that simple numerical modeling techniques can lead to an accurate prediction of the displacement response of the bridge seismic protective systems studied.

A disastrous earthquake struck Wenchuan in China’s Sichuan province in 2008 and caused heavy casualties and structural damage to bridges and buildings. One of the two severely earthquake-damaged curved bridges in China, the Huilan interchange, had been carefully studied, including postearthquake investigation and identification of the cause of failure for this bridge. The Huilan interchange, constructed in 2004 in Mianzhu City, consisted of a viaduct and four horizontally circular ramp bridges with continuous box girders. Field investigations found that the seismic damage to the ramp bridges was especially heavy, one or two short piers in all, but one of the ramp bridges experienced severe failure, and the box girders over the failed piers were fractured. Other piers of the ramp bridges suffered minor-to-moderate damage, including concrete cover spalling, concrete cracking, and slippage damage of the rubber bearings. The viaduct suffered only slight damage, including slippage damage of the rubber bearings and pounding damage of the superstructure. The seismic performance of the bridge was evaluated by finite-element modeling and compared with field observations. It was found that the bearing on top of the shortest pier, Pier 1, was damaged first. Then, the seismic action was concentrated on the next shortest pier, Pier 2, which had the largest flexural stiffness. Pier 2 first yielded in flexure, and, as the lateral displacement increased, the ultimate response of this pier was dominated by its shear capacity, and it eventually failed in flexure-shear mode.

Structural fuses, easily replaceable sacrificial elements to dissipate seismic energy while preventing damage to the gravity load-resisting structural system, are proposed as part of a multicolumn accelerated bridge construction (ABC) pier concept. Different types of structural fuses are investigated to compare the effect of each on ABC bridge bents. The piers of a three span-continuous bridge prototypes having two twin-column pier bents were designed using double-composite rectangular columns and structural fuses. Two corresponding $2/3$ -scale models were developed and were subjected to cyclic quasi-static tests. For the first specimen, steel-plate shear links (SPSLs) were installed between the columns as a series of structural fuses. Testing was performed, first up to a drift corresponding to the onset of columns yielding to investigate the effectiveness of adding the fuses in dissipating the seismic energy, then up to failure of the composite columns. The second tested specimen has buckling restrained braces (BRBs) as a series of structural fuses between the columns. The BRBs were then removed, and a cyclic test of the composite bent continued until failure of the columns. Both specimens exhibited stable hysteretic behavior, with the structural fuses also increasing stiffness and strength of the bent. Individual testing results for the SPSLs with various geometries and boundary conditions are then presented.

This paper presents the results of an analytical investigation conducted to replicate experimentally obtained behavior, and better understand the behavior of the proposed structural fuse concept for bridges that is presented in a companion paper. First, a steel plate shear link (SPSL) proposed as a new type of structural fuse is described. Equations are derived to define its shear-moment interaction equation, to determine some of its critical design parameters, and to quantify the link ductility, lateral stiffness and strength. Strengths and stiffnesses equations are developed using free-body diagrams (FBDs) for the tested systems as a convenient simple design tool. Finite-element models (FEM) are developed by using the finite-element software package ABAQUS/explicit to validate the proposed SPSL concept, and then to replicate the full range of results obtained from the experiments. Comparisons between the analytical and experimental results are conducted to highlight the differences in behavior among all tested specimens. The simple numerical equations correctly represent the expected strengths and stiffnesses of the fuse systems. Further, the results obtained from the ABAQUS model accurately captured the global behavior of the system, and provided valuable insight into individual fuse behavior.

It is well known that wind loads result in wind-induced buffeting of slender long-span bridges. Traffic also frequently exists on a slender long-span bridge simultaneously throughout its service life, which can affect the dynamic behavior of the slender structural systems. The nature of the vibration of a slender long-span bridge is further complicated by the dynamic coupling effects among the bridge, wind, and traffic. Fatigue damage is an important consideration in the serviceability performance of slender long-span bridges that typically experience cyclic or repetitive loads, such as those induced by wind and traffic. Stochastic wind and traffic loads, dynamic interaction, and fatigue accumulation for a slender long-span bridge essentially vary over time, with uncertainty contributions from each. Therefore, a reliability-based fatigue assessment model, which can rationally consider the combined load effects from wind and traffic as well as the associated uncertainties, is needed to provide an accurate estimate of reliability for fatigue. Initially, a scenario-based deterministic fatigue analysis model is developed. A typical year is categorized into several representative scenarios of traffic and wind conditions. After identifying the duration for each representative scenario in a typical year, a cumulative yearly fatigue damage factor can be predicted by superposing the cumulative hourly damage factors for all representative scenarios. On the basis of the scenario-based deterministic analytical model, the framework of the reliability-based fatigue damage assessment for a slender long-span bridge is further developed. Finally, an illustrative example for a prototype bridge is conducted.

This paper focuses on estimating the fatigue life below the constant amplitude fatigue threshold (CAFT) of steel bridges by using a probabilistic approach on the basis of a bilinear stress life (i.e., the $S\mathrm{\text{-}}N$ approach). The current AASHTO $S\mathrm{\text{-}}N$ approach uses a single $S\mathrm{\text{-}}N$ line for predicting the fatigue life. However, because of the variation of actual applied live-load stress cycles, this approach very often results in a severe underestimation of the useful life of structures. It implies that fatigue damage in respective structural steel details may be overestimated. To improve fatigue life estimation, a bilinear $S\mathrm{\text{-}}N$ approach is integrated into a probabilistic framework that can model the uncertainties associated with the fatigue deterioration process. In this approach, the equivalent stress range is computed by using two $S\mathrm{\text{-}}N$ slopes and several probability density functions associated with stress ranges. These probabilistic functions are determined on the basis of stress-range bin histograms from long-term monitoring. An existing bridge that is expected to experience finite fatigue life is used to illustrate the application of the proposed approach.

Load-rating factors are used to evaluate the service life or safety of culverts based on the culvert wall strength and soil cover depth over the culvert. Current culvert load-rating methods have deficiencies in identifying potential critical conditions of corrugated metal culverts. Current load-rating procedures do not provide explicit guidance to the engineer for load rating and evaluation of culvert condition. To ensure good performance over the design life, corrugated metal culverts must be designed and regularly evaluated using an effective load-rating method. The main objective of this study was to investigate the effectiveness of current load-rating procedures. Recommendations are made to improve the analysis and evaluation procedures for corrugated metal culverts. The proposed load-rating procedure is based on an extensive review of load-rating procedures and design practices, experimental data, and theoretical investigations. The proposed method does not include a rating factor for cover depth. However, the design cover depth is required to be checked during the initial design stage to ensure structural stability. New capacity reduction factors are introduced for culvert wall and seam, which require different appraisals for wall and seam during annual inspections. The effect of external live loads is not included in the proposed load-rating procedure for deep culverts and for culverts subjected to low live load stresses. Field data from 39 in-service culverts showed that the proposed load-rating procedure is effective in evaluation of the existing condition of culverts.

Deep-corrugated steel culverts (corrugation wavelength of 400 mm and amplitude of 150 mm) can be effective alternatives to short-span bridges. Because the corrugation dimensions are of a similar size to their minimum burial depths, the effectiveness of conventional orthotropic shell theory in soil-structure interaction analyses needs to be studied. Results from a large-scale laboratory test are therefore reported on a 10-m-span structure responding to a pair of vertical loads placed along the crown before burial. This test is then modeled by using three-dimensional finite-element analysis by using two different approaches. The first is on the basis of explicit modeling of the corrugated structure, whereas the second is on the basis of orthotropic shell theory. Comparisons are then made between the two sets of calculations and measured values of displacement and circumferential strain, and moment and thrust are calculated from measured strain. The corrugated analysis produced estimates of displacement at the center of the structure within 0.2% of measured values, whereas the orthotropic shell analysis yielded an error of 4%. The corrugated analysis provided strain values much closer to those that were measured. Moment and thrust values from the corrugated analysis were within 3 and 2% of the experimental values, respectively, whereas values from the orthotropic analysis erred by much greater amounts, particularly in the vicinity of loading points in which the orthotropic analysis cannot model local effects. Finally, the use in design of both explicit representation of the corrugated geometry and orthotropic analysis are discussed.

Continuous bridge decks constructed with precast girders undergo significant stress changes caused by the concrete delayed deformations because of creep and shrinkage. These effects must be taken into account in the design of new structures. The validation of the analysis procedures should ideally be carried out through the comparison between the calculations and the results observed in real structures. However, experimental results of the construction and long-term behavior of these structures are scarce. The construction of a major bridge in Portugal has provided the opportunity to monitor one such structure. This paper presents the monitoring campaign and the analysis strategy that was developed to assess the long-term variation of strains and stresses in precast continuous bridges. The numerical analysis was validated by comparison with the results observed in the real bridge. The consequences of carrying out simplified analyses based on limited information about the concrete properties and the construction sequence are also evaluated.

Most of the movable bridges in the United States have open grid steel decks, primarily because they are factory assembled, lightweight, and easy to install. Open grid steel decks, however, are not as skid resistant as solid decks. Costly maintenance, high noise levels, poor riding comfort, and susceptibility to vibrations are among the other disadvantages of these decks. The objective of the research presented in this paper is to evaluate an alternative lightweight extruded aluminum deck system that has a solid surface and meets the loading requirements as well as weight and thickness limits for movable bridge decks. These aluminum deck panels with their tongue and groove connections have previously been used in Europe, mainly in Sweden. A detailed experimental evaluation of the aluminum deck system has been carried out, including static and fatigue load testing on the deck panels, as well as ancillary tests on the connections with the girders. On the basis of the in-depth experimental evaluation and the subsequent finite-element (FE) modeling and predictions, the extruded aluminum deck is shown to be a feasible alternative to the open grid steel deck and ready for implementation on movable bridges as well as bridges that require a lightweight deck.

The tied arch bridge system provides a unique solution to the several challenges associated with the construction of railroad overpasses and water crossings, such as restricted vertical clearance, undesirable or impractical arrangement for intermediate piers, and extremely limited traffic control during construction. The paper presents the design and construction challenges pertinent to a novel concrete-filled steel tubular tied arch system that was first introduced in the Ravenna viaduct (53 m) and applied later to the Columbus viaduct (79 m). The main structural components of the Columbus viaduct are described in detail and the advantages of the system are summarized. The detailed analysis of the system at different construction stages and design checks of main components and connections under various loading conditions are discussed. Experimental investigations conducted on concrete-filled steel tubular arch and tie specimens to validate their theoretical capacities are demonstrated. The three-dimensional nonlinear finite element model developed to analyze the tie-to-arch connection and evaluate the lateral stability of arches is presented. Finally, the main construction procedures and challenges of the three tied arches of the Columbus viaduct are highlighted.

In this paper, a general framework for the optimal resilience- and cost-based prioritization of interventions on bridges distributed along a highway connection between two cities that have experienced a disruptive natural or man-made event is proposed. Given the structural damage levels after the extreme event and the bridge characteristics, the proposed computational procedure finds the best intervention schedules, defined as starting time and progress pace of the restoration. The possible intervention schedules are considered optimal when they maximize the resilience of the highway segment and minimize the total cost of interventions. Because the two objectives are conflicting, the procedure uses genetic algorithms (GAs) to automatically generate a Pareto front of optimal solutions. Numerical examples are presented and discussed.

A baseline finite element model was developed for bridge management and calibration using nondestructive test data. The model calibration technique was evaluated on the Vernon Avenue Bridge over the Ware River in Barre, Massachusetts. This newly constructed bridge was instrumented throughout its construction phases in preparation for a static truck load test performed before the bridge opening. The strain data collected during the load test was used to calibrate a detailed baseline finite element model in an effort to represent the 3D system behavior of the bridge. Three methods of load ratings were used and compared: (1) conventional method, (2) conventional method updated by using NDT data, and (3) finite element model calibrated with NDT data.

The paper presents a case study for comparing the seismic rehabilitation of four reinforced concrete multicolumn bridge bents typical of older bridges not designed for current seismic code criteria. The types of intervention included connecting the piles to the pile caps with high-strength prestressing steel bars, widening of an existing strut beam connecting the pile caps, construction of a new reinforced concrete grade beam overlay to connect the pile caps, and carbon fiber reinforced polymer composite jackets for strengthening the columns and cap-beam-column joints. The paper includes the hysteresis curves from in situ experiments in which a lateral quasi-static cyclic load was applied at the cap-beam and comparisons to analytical pushover curves. A comparison of the capacity of the four bents to the demand of several earthquake records including historical and NEHRP design earthquakes is developed. The cost of seismic rehabilitation of the four bridge bents is presented along with the peak maximum lateral load and maximum displacement achieved in the experiments. The cost of the seismic rehabilitation is related to the performance of each bridge bent. The bridge bent with the lowest level of intervention had the lowest cost and met the displacement and base shear demands for the 10% in 50 years NEHRP design earthquake; the bridge bent with the highest level of intervention had the highest cost and met the displacement and base shear demands for the 2% in 50 years NEHRP design earthquake.

The dynamic response of a three-span reinforced concrete deck on steel girder skew bridge supported by elastomeric bearings is investigated both experimentally and analytically. The case study presents modal parameter estimates obtained from a large-scale field deployment of accelerometers supported under a wireless sensor network. Through output-only system identification, the natural frequencies, damping ratios, and mode shapes are extracted for the first 20 structural poles. Linear dynamic analysis of the bridge through three-dimensional finite-element analysis is then performed to provide a comparison between the response estimate predicted under the minimum requirements of multimode spectral analysis dictated by the AASHTO design specifications and the in-service dynamic response. Linear elastic bearing stiffness in the compressive, shear, and flexural states is estimated using independent design specifications set forth by AASHTO and Standards Australia, and modeled with idealized fixity. The case study concludes that linear dynamic analysis provides a well-correlated, yet conservative estimate of multimodal displacement for bridges supported by steel-reinforced elastomeric bearings when bearing stiffness is defined by using either design specification.

The tension force of cables must be measured accurately during construction and maintenance stages for cable-supported bridge systems. On the basis of the transverse vibration equation of a cable and by using a curve-fitting technique to replace the numerical iterative process, a practical formula to estimate the cable tension is proposed in a simply explicit form, in which the bending stiffness of the cable is included, and the sag effect is neglected for simplicity by using the frequencies relative to antisymmetric or higher vibration modes of the cable. The capability of this formulation is verified through comparison with available experimental results and finite-element solutions, which indicate that the formula developed in this paper is sufficiently accurate and can be conveniently applied to field measurement for cable-supported bridge systems.

The skew angle affects the geometry and design of a bridge in many ways. For example, skew angles greater than 20° will affect the bending moment and the shear force in an exterior beam. The U.S. Army Engineer Research and Development Center performed a full-scale load test on a skewed railroad steel truss bridge at Fort Leonard Wood, Missouri, in July, 2007. The superstructure of the bridge was instrumented with 42 reusable strain transducers to accurately measure the structure’s response to a 260 kip train engine. Analyses were carried out to determine the effect of the skew angle in that response. A three-dimensional finite-element model (FEM) was developed from the data collected during the load test. The measured internal axial forces compared satisfactorily with the results from the FEM analysis. After the calibration of the model, the results indicated that the skew angle decreased the internal axial forces by approximately 16%, which was comparable to current design practice.

This technical note presents the computations, results, and conclusions of an analytical investigation for comparing the life-cycle cost (LCC) of a steel bridge component made of a new maintenance-free steel and the LCC of the same steel bridge component made of conventional painted carbon steel with maintenance (repainting). An approach for the LCC analysis is presented both deterministically, where different painting scenarios are considered, and probabilistically, where the uncertainties in the input variables are properly considered. Under reasonable cost assumptions, it is demonstrated that the new steel, although initially more expensive, is indeed cost-effective after approximately 15 years. The LCC-effectiveness of the new steel increases over the service life of the bridge component.

Bridges with unknown foundations have been a burden on the transportation agencies across the United States because of the lack of funding and availability of rational methods to determine the risk of failure of these bridges from scour. The embedment of unknown foundation bridges is a key to proceed further with any risk-based management approach and/or the widely used Federal Highway Administration (FHWA) guidelines on the methods of evaluation of unknown foundations. The need for a practical, cost-effective, and rational approach to positive discovery of bridge foundations and to reclassify bridges with unknown foundations is greater than ever. This technical note presents an assessment of the predictive capability of various methods currently in use to determine the embedment of unknown foundation bridges. The methods discussed in this paper include sonic echo method (or pile integrity tester) as non-destructive testing (NDT), inference (IM) and/or back calculation (BC) [i.e., reverse engineering (RE)], and static/back calculation (S/B-C). The well-documented case histories presented in the paper illustrate the usefulness of using the S/B-C method in determining the embedment of unknown foundations. The S/B-C also can be used to assess/validate NDT results and embedment estimates made by IM and/or BC (RE) approaches. For high priority unknown foundation bridges, the S/B-C reasonable minimum embedment and the embedment required for stability considering the scour can be used to plan and efficiently implement any future NDT for these bridges. It can significantly reduce the cost of treating unknown foundation bridges by optimizing the use of NDT, if warranted. The three case histories presented in the paper also suggest that, in general, the sonic echo (i.e., pile integrity tester)/NDT tends to be conservative whereas the IM and/or BC (RE) methods tend to be unconservative. This would lead to high cost or high risk, respectively, if such estimates are used to assess the stability of unknown foundation bridges impacted by scour.